FLAME-SENSING FIRE ALARM Using An Arduino Nano

Fire safety alarms are crucial in both residential and industrial environments.

- SURESH CHANDRA DWIVEDI

Early fire detection can prevent significant damage and save lives. Flame sensors offer one of the most efficient methods of fire detection. Here we outline how to construct a simple and reliable fire alarm system using a flame sensor and an Arduino Nano board.

This fire alarm is intended for hobbyists and individuals interested in learning the basics of electronic sensors and alarms. The simplicity of this device can pave the way for creating life-saving systems. Fig. 1 shows the author’s prototype on a breadboard.

Circuit and working

Fig. 2 presents the circuit diagram for the fire alarm using a flame sensor and Arduino Nano. The system is powered by a step-down transformer (X1), a bridge rectifier (BR1), a 12V voltage regulator (LM7812), and a flame sensor module connected via CON2. It includes a 12V SPDT relay (RL1), three LEDs (LED1 through LED3), and two transistors (BC548 and SL100), along with some other components.

The circuit operates on 12V DC, which is derived from the 15V, 500mA secondary output of transformer X1. The 230V AC mains supply connects to the primary of X1 through connector CON1. On the secondary side, the 15V AC is rectified by BR1, filtered by capacitor C1, and regulated to 12V via IC LM7812 to power the circuit.